Claims about the success of brainstorming rest on easily tested assumptions. One assumption is that groups produce more ideas than individuals. Researchers in Minnesota tested this with scientists and advertising executives from the 3M Company. Half the subjects worked in groups of four. The other half worked alone, and then their results were randomly combined as if they had worked in a group, with duplicate ideas counted only once. In every case, four people working individually generated between 30 to 40 percent more ideas than four people working in a group. Their results were of a higher quality, too: independent judges assessed the work and found that the individuals produced better ideas than the groups.

Follow-up research tested whether larger groups performed any better. In one study, 168 people were either divided into teams of five, seven, or nine or asked to work individually. The research confirmed that working individually is more productive than working in groups. It also showed that productivity decreases as group size increases. The conclusion: “Group brainstorming, over a wide range of group sizes, inhibits rather than facilitates creative thinking.” The groups produced fewer and worse results because they were more likely to get fixated on one idea and because, despite all exhortations to the contrary, some members felt inhibited and refrained from full participation.

I concur with this based on 15 years in the design and advertising industries.

In brainstorming sesssions—as in life—there’s a couple of winners and a whole lot of losers.